The translational dynamics of specific cell membrane components will be studied with particular emphasis placed on the systematic transport processes associated with active cell locomotion. A variety of modern optical methods will be used, principally the recently developed fluorescence photobleaching recovery. In this technique, transport rates are determined by monitoring the recovery of fluorescence in a small region of the cell surface initially photobleached irreversibly by an intense focused laser light pulse. The implications of cell locomotion to the invasiveness of neoplastic cells, the resistance to infection, and to embryonic development will be explored in a variety of systems. Experiments continue on randomly locomoting primary and secondary fibroblasts in culture, probing for differences in structural dynamics between normal and neoplastic cells. Other projects will investigate the roles that plasma membrane dynamics may play in the response of neutrophilic polymorphonuclear leucocytes (PMN'S) to chemotactic gradients, and the development of PC12 cells in response to nerve growth factor (NGF). Finally, as a further approach to an understanding of the factors that influence membrane fluid dynamics, studies will be conducted on model membrane systems, supplementing the work on whole cells in culture.